الفهرس 
Basics of the nuclear radiologyOnly 14 pages are availabe for public view
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Abstract
Nuclear radiology is a branch of medical imaging that uses radiopharmaceuticals to examine the function and structure of organs and tissues. It plays an important role in the diagnosis of bone metastases. The sensitivity of nuclear radiology techniques is remarkably high, exceeding 90%. The main difference between nuclear imaging and other radiologic tests is that nuclear imaging assesses how organs function, whereas other imaging methods assess anatomy.
The normal process by which osteoclasts and osteoblasts destroy existing bone and form new bone is called bone remodeling. Bones are continually remodeled as a mechanism to maintain skeletal strength and integrity. The bone remodeling cycle is regulated by a variety of systemic and local factors. The three essential regulatory components of osteoclast metabolism are osteoprotegerin (OPG), receptor activator of nuclear factor NF-kB ligand (RANKL), and receptor activator of NF-kB (RANK).
Metastases have been characterized either osteolytic or osteoblastic, Patients can have both osteolytic and osteoblastic metastasis or mixed lesions containing both elements. In osteolytic bone metastases, there is a tumor-produced paracrine factors, such as parathyroid hormone-related protein (PTHrP) and IL-6, often are responsible for the osteoclast-stimulating activity and the bone destruction. Osteoblastic lesions are the result of the production of soluble paracrine factors by the tumor cell that stimulate bone formation by increasing osteoblast activity. Bone metastases can be diagnosed by clinical presentation, laboratory tests and radiologic methods. Plain radiographs are commonly used to evaluate symptomatic areas. Because of its poor sensitivity. it is generally not used as a screening method. CT demonstrates superior bony detail. Osteolytic, osteoblastic and mixed bone metastases are well despicted on CT. MRI can provide detailed imaging of the bone and bone marrow. It is highly sensitive (with a sensitivity ranging from 82% to 100%) for the detection of metastasis because of its ability to demonstrate marrow abnormalities. skeletal scintigraphy is the preferred initial imaging modality in cancer patients at high risk of bone metastases. Bone scan has published sensitivity rates between 62% and 100%.
PET is characterized by high-contrast resolution, whole body tomographic data. Using the various PET tracers, functional changes occurring in the bone marrow and bone as a result of malignant infiltration may precede the structural changes.
18F-Fluoride PET is not a routine imaging modality for detecting malignant bone involvement. Its use is primarily suggested in patients at high risk for metastatic bone disease, that is, if bone metastases are suspected clinically and bone scintigraphy is negative.
PET/CT may take advantage of the high sensitivity of 18F-Fluoride PET, reducing the risk of false positive rate by determining the morphology of the scintigraphic lesions on the CT data. PET/MR offers potential advantages over PET/CT for evaluation of bone lesions, Because of its higher soft-tissue contrast. Evaluation of tumor response to treatment with FDG PET has several advantages over anatomically based criteria. By reflecting change in tumor metabolism, FDG PET scanning can provide a method by which tumor response can be measured in the absence of marked anatomic change.